chemistry yeild of water?

Question

Ammonia reacts with diatomic oxygen to form nitric oxide and water vapor:

4NH3 + 5O2 ® 4NO + 6H2O
What is the theoretical yield of water, in moles, when 40.0 g NH3 and 50.0 g O2 are mixed and allowed to react?

Answer 1

Molar ratios are
NH3 : O2 : NO : H2O :: 4 : 5 : 4 : 6
Mol(NH3) = 40/17 = 2.3529
Mol(O2) = 50/32 = 1.5625
We need to find the limiting reagent. So divide through by smallest ratio.

NH3 = 2.3529/1.5625 = 1.5058
O2 = 1.5625/1/5625 = 1
As oxygen is in the smaller ratio it is the limiting reagent.
Ammonia is in excess.
So mol(O2) = 1.5625 is equivalent to 5
therefore Mol(H2O) = 1.5625 x 6 /5 = 1.875
Mass(H2O) = 1.875 x 18 = 33.75 g (theoretical 100% yield).